I'm a night owl who exercises after dinner. Does this affect my workout?

The biggest risk you run from squeezing in sweat sessions post-meal: stomach cramps. In order to digest food, your body pumps blood to your gut, explains Michael Fingerhood, M.D., associate professor of medicine at Johns Hopkins University in Baltimore. But exercise redirects that blood flow to your muscles, which can cause your stomach to spasm. Wine drinkers, take note: Of the doctors we polled, none would toast to having more than 4 ounces before physical activity. Any more and not only could you slip or trip, but you're also much more likely to get dehydrated.

Bottom line: You could forgo your after-dinner session for an earlier lights-out and sweat in the A.M. But if nighttime is your only window, stick with it. Have a snack (such as a piece of fruit) 30 minutes pre-workout if you're hungry, then eat dinner (and sip your wine!) once you've kicked off the sneakers.